When writing a linear novel, my current planning process is what I’m calling orienteering. It is basically a planner’s version of flashlighting.
Basically, I worldbuild, create characters, and develop the overall shape of the world, major landmarks (key scenes, moments, or realizations), and the route I want to take. I do not plan every plot point or scene. Instead, I have a few paragraphs summarizing everything. Then, I divide that long route into small chunks (think days of travel) and I plan out one chunk at a time. I figure out which scenes need to happen in that chunk to get me from start of the chunk to its end. I use my map (the paragraph summaries and everything else) to guide me. Sometimes, while writing, I’ll realize of an interesting alternative route or I’ll notice an unexpected landmark, etc. The journey changes from my expectations, but I still reach my eventual destination.
For IF, what I’ve done is identify my plots. For my main plot, I listed out around 8 to 10 realizations the player / character needed to have. I’ve distributed those across the chapters. Then, for each side plot, I listed out the problem, potential solutions, and key scenes for each. The side plots also shape the world, giving more shape to the chapters. Even if you don’t engage with the political plot, the politics are still happening.
I’ve also decided to try a learn-explore-act system of scenes (described here). I’m using these scene types to create buckets more or less. So, when I reach chapter 3, I know I need an explore beat for the shadow plot and a learn beat for the guild plot. Etc. I’ve not detailed what those scenes should be. I’ll fill the buckets when I reach them.
Ultimately I’ve learned that I need a structure that allows a lot of flexibility and I do best when I can define the parameters/etc ahead of time, but fill in all the details as I go. Plus, I like having the ability to change parameters as needed, though I rarely change where I’m ultimately going.